Abstract

Soluble tumor antigen was prepared from two transplanted sarcomas of strain 13 guinea pigs, induced with 3-methylcholanthrene or 9,10-dimethyl-1,2-benzanthracene, by extraction with isotonic saline followed by ultracentrifugation. Further fractionation by ammonium sulfate precipitation, gel filtration on Sephadex G-150 or Biogel A-5m, and DEAE Sephadex chromatography was performed. Antigenic activity was assayed in vivo by skin tests and in vitro by the macrophage migration inhibition method. Antigenic activity was not restricted to a single species of molecules as defined by size or charge. The major part of the activity was associated with two fractions, one excluded by Sephadex G-150, and the other included in Sephadex G-150. The behavior of the antigen preparations in isopycnic sucrose gradient centrifugation indicated that they were truly soluble and not membrane associated. The active fractions were nontoxic for the skin and for peritoneal cells and stable under the conditions of the macrophage migration test. Their antigenic activity was specific for each of the two tumors. In terms of the amount of antigen required to give a positive reaction, the migration inhibition assay was more sensitive than the skin tests.